System of radiocommunication



June Z3, 1925.

H.'A. BREMER l SYSTEM oF RADIOb COMMUNICATION Filed Dec. 1,1924

\ l n lm 1li l wlws'cription.

Patented June 23, 1925.

UNITED STATES Y l 1,543,417 PATENT OFFICE.

I-IAIELRY A. BREMER, OF CHICAGO, ILLINOIS, ASSIGNOR TO BREMER-TULLYMANUFAC- FURING COMPANY, OE CHICAGO, ILLINOIS, A. CORPORATION OF ILLINOIS.

SYSTEM or RADIocoMMUNIcA'rIoN.

Application 'filed December 1, 1924. Serial No. 753,147.

To all whom Tt/map concern.'

Be it knownfthat I, HARRY, A.'BREMER, a citizen of the United States,residing at Chicago, in the county 'of CookffandY the State of Illinois, have invented a certain new vand useful Improvement, in Systems of Radiocomm-unication, of which the following is a full, clear, concise, and exact de- My invepaonf'relates to radio communicationv andi'iesides in the' provision of improved means for compensating for or offsetting undesired v'feed back effects.

It is well known that resonant thermionic valve input and outputcircuits of low resistance are desirable'for' the vbest operatrolling oscillation.

tion of an amplifying thermionic valve. However, the bringing of the output circuit into resonance with the input'l circuit of such a valve tends to produce oscillation. Decreasing the resistance of theinput circuit also tends to favor oscillation.

-In order to secure the advantages of low resistance tuned circuits, it is necessary tfemploy some means for preventing or con- Methods -now` ployed for this purpose require consider.- able readjustment for changes infrequency or ,wave lengthsy or fail when the resistances of the circuits are reduced to a low valuel l lThe system of" my invention employs a bridge connecting the input and output circuits of' a thermionic valve and including means serving to oppose the feed back effect of the output circuit upon the input circuit. Inv the preferred4 embodiment of the-invention,'I employ an input transformer having a secondary in the input -circuit, an output transformer having a primary in the output circuit, two coils in the bridge, one being in inductive relation to said input transformer secondary and serving to opposethe feed back effect of the output circuiton the input circuit and the other being in inductive relation to said output transformer primary and furnishing a compensating feed back effect, and. adjustable capacitancein said bridge.

The invention wi ll be more fully eX- plained in connection with the accompanying drawing which is a diagrammatic illustration of the preferred embodiment thereof.

to ground 3. The secondary 4 of the coupler and the variable secondary tuning condenser 5 in shunt'relation thereto, are also traversed by radio frequency current. The radio frequency amplifying tube or thermionic valve@ includes a grid l7 that is.

Afrequency transformer. A secondary 14 thatis individual toithe primary 13 supplies amplified radio frequency current to a-circuit' which includes the grid 15 of the thermionic valve 16, there being a variable Ycondenser `17 included in a bridge between'the sides of the secondary circuit containing the winding 14. The thermionia valve` /16- includes the usual heating filament 18 in va local circuit `with the A battery 11 andthe rheostat 19 which controls the heating effect of .this filament. Current is received by the plate or electrode20 of the valve 16Y and is supplied 'to the primary 21 of anV air coretransformer, the secondary 22 of this transformer supplying audio frequency current to the input grid 23 of a rectifyingthermionic valve 24 by way of the condenser 25 which is bridged by a leak 26. Valve 24 includesthe usual heating fil` ament 28 whose effect is controlled by thc usual rheostat 29. The secondary 22 is shunted'by a variable condenser 27. The rectified audio frequency current is received by the .plate or elect-rode 30 and is supplied to the telephone or other receiver 31.

A bridge 32 (shown by heavy lines for clearness)"is connected at one end between the plate. 2O 'of the valve 16 and the primary 21 which is connected with this plate.'

The other end of this bridge is connected with the'end of thesecondary 14 which is connected with the filament 18. The bridge llO vment of the control. back 1s secured by `means of the variable condenser which acts `as a variable couadjustable capacitance 35 is included in the bridge between the coils 33Y and 34.

fThe inductive relation of coil 33 to coil 414: is such as to oppose the feed back effects of the output circuit on the input circuit of the valve 16. y

The combined direct plate potential and inductive action of coil 21 on coil 34 tends to produce a compensating feed back which whenl coupled inductively to coil 14 through oppose the feed back coil 53 permits operation of the valve just below the point of oscillation over a large variation of frequency without readjust- Adjustment of feed pling between coil 33 `and the. coils 2l, 34.

The compensating coil 34 tends to correct i the variation of adjustment for various wave lengths.

In. an equipment lacking my invention,` the receiver may be adjusted by condenser 35 so that it becomes sensitive at short wave lengths, as two hundred and twenty ineters.

Considerable readjustment of condenser 35.

is necessary at fixe-hundred meters to bring the tube back to the same sensitivity. By employing the coil Sil as set forth, it is possible to maintain the sensitivity of the circuit from two hundred to five hundred meters, for example, with only very slight adjustment of condenser 35. lf this ccn-- denser is given a permanent a wave length of, say, two hundred and twenty meters, the circuit will be much more sensitive at five hundred meters, for

example, than if the prior method were used.'

Bysensitivity is meant just below and remaining at the point of oscillation for the tube for a considerable range of wave lengths, a condition realized by the compensating acti'o'n of the coil 34.

Adjustment is requiredas wave lengths vary because capacity and inductive effects vary considerably as wave lengths vary. Coil 34, when close coupled to the plate coil S21 and connected in the plate shunt circuit, as shown, compensates for this variation.

Changes may be made without departing from my invention.

Having thus described claim 1. ln a radio system of communication, the combination with a thermionic valve having an input circuit and an output cirmy invention, l

the input adjustment at vthe combination with a inductive relation .transformer primary and supplying it to the first coil for this purpose; and able capacitance' in said bridge.

2. In a radio system of communication, the combination with a thermionic valve having an input circuit andan output circuit; of an input transformer having a secondary in;A said input circuiti an'output transformer having ,af primary in'said output circuit; a bridge conr'iectirigl said cir-- cuits and including two coils-,one being in inductive relation Ito VtheI said input transformer secondary and theother being in'ii1` ductiye relation to said output. transformer. primary, the' first coil opcrating'through transformer secondary to opposeA the feedback effect of the output circuit adjustderiving potential from the output transformer primary and supplying it to the first coil for this purpose; and a variable c'ou'- pling between the coils in said bridge.

8. In a radio system of communication,

having an input circuit and an output c1r. cuit; of an input transformer having athermionic valve secondary in said input circuit; an' output i transformer having a primaryin sa1dcutput circuit; and a' bridge connecting said circuits and including two coils, one being iii inductive relation to the said input trans;- former secondary and the other being in` K to said output transformer primary, ,the first coil operating through the input transformerV secondary to oppose the feed back effect of the output j circuit upon the inputfcircuit and the' second coil deriving potentialv from the outv put transformer primary and .supplying it to the first coil for this purpose.

ln witness whereof, l hereunto subscribe my name. 

